GM HVAC on the GMLAN

[ScottyhsvR98]

Hey lads,

Im sure this has probably been asked before but Ive searched and searched and could find the exact help that I need..

I have a 2007 VE Clubsport and a couple of years back my infotainment system decided to stop working so instead of getting that seen to installed a custom Head Unit with an Aerpro Fascia everything was going ok until it decided to give up on my A/C and wouldnt work anymore and with it being out of warranty I just left it, since then I been working on my own android climate control app now ive got the app pretty much sorted but its the SWCAN frames I just cant seem to send the correct frames that the HVAC module is looking for to get anything working ive been over and over the GMLan Bible and the GWM3010 doc.
My kinda understanding is that the fascia only needs to send 3 frames the 0x71 Climate Controls Buttons 0x72 Left Temp Dial 0x73 Right Temp Dial. I have been using an ESP32S3 Dev Mod with an NCV7356 Single Wire Can Transceiver and ive also tried with the OPDXPROGT running on the bus and sending 11bit frames both work fine at receiving the swc frames but transmit is just getting ignored, it also seems like HVAC is on the bus and sending frames yet another thing im unsure about is my OBDXPROGT, TECH2, Vident iAutoPro cant reach the module and they all come back saying no comms with it...
So im stuck in nomans land with no idea how to go about fixing it..

Thanks in advance

[kur4o]

You did a fundamental error. Assume it should work like that without actual communication log, what triggers the AC.

Find a working module that commands AC and do some real logs, than test commands and you are set.

[Tazzi]

Ahh... I believe the broadcast data that you are referring to is 29bit gmlan.

For instance, I click a button on the radio to change aircon settings, this sends out a 29bit CAN frame that the HVAC picks up and manipulates.

It looks like what you have mentioned, 0x71,0x72,0x73 is referring to ArbID's which is not the full 29bit CAN frame, its only a portion of the ID.

Never work off ArbIDs, always work off full IDs.

[Staggie]

From a conversion I did I purely wanted to trigger the system on/off using the hvac module from the donor, also has other parameters like fan speed, vent and temp but you will need to map them out.

ID 0x100E2080
AC on 0x00, 0x40, 0x04, 0xC0, 0x04, 0x7F, 0x00, 0x00
AC off 0x00, 0x00, 0x04, 0xC0, 0x04, 0x80, 0x00, 0x00

[ScottyhsvR98]

Thanks for the replies lads. Im kinda flying blind without having a setup to be able to sniff the bus while pressing the buttons. Ill upload a log i took when i get home and the code im using so you can check it out and see where im going wrong. Everything ive been reading says you have to do it this way then the next thing. I read says its gotta be done that way. Im only a novice when it comes to canbus but i guess its a place to start right in the deep end lol.

[ScottyhsvR98]

Here's a fresh log i took just now RX all frames..

[Tazzi]

If there is an aircon related issue, this can also cause the A/C to not work correctly.

So with that in mind, plug in a factory radio and check it is all working correctly first before trying to make an app, just to eliminate that mess.

The reason I say that is even if you send the correct A/C request to the HVAC (simulating button click from radio to HVAC), the HVAC will reject it if it believes there are aircon related problems or also can be rejected if the ECM does not want to allow it (For whatever reason).

[ScottyhsvR98]

Just to give you guys an update I have found the problem of no comms to the hvac module and not seeing any frames from it its because I currently have B1000 33,36 DTC’s EEPROM integrity and Special Performance Memory blah blah meaning that the BCM is not acting as the gateway and not letting the IPC send the ignition state frame to power up the HVAC Module. Hopefully the commodore shop up the road has one the part number is 15948439 and I have a list of confirmed hardware compatible numbers so fingers crossed. Once I’ve reprogrammed it ill give you another update on whats happening on the GMLAN my guess is a lot more than what im seeing now. I did replace the EEPROM with a new S93A66 flashed with my bin i backed up quite a while ago and its still giving same error so i think its cactus.

[ScottyhsvR98]

Update:: Replaced with a 2nd hand unit flashed the EEPROM with the backup of mine. All is good the electrical shit is all fixed Parking Senors back, all lights, windows and doors not playing up anymore BUT still no HVAC module comms ive tried 2 other modules same thing its getting signal on the GMLAN pin its getting Batt+ from the big blower cables what else could it be. Am i right in saying it gets the power state/wake up from the IPC could it be that im lost now. Dunno what else to try.